Microstructural development of Si3N4–SiC–Y2O3 ceramics derived from polymeric precursors

1998 ◽  
Vol 13 (2) ◽  
pp. 353-361 ◽  
Author(s):  
Yuji Iwamoto ◽  
Ko-ichi Kikuta ◽  
Shin-ichi Hirano
Keyword(s):  
Heat Treatment ◽  
Aspect Ratio ◽  
High Aspect Ratio ◽  
Hot Pressing ◽  
Microstructural Development ◽  
Polymeric Precursors ◽  
Fine Grained ◽  
Chemically Modified ◽  
Amorphous Powders

[Si–Y–O–C–N] amorphous powders were synthesized by the pyrolysis at 1000 °C in N2 of chemically modified perhydropolysilazane using n-decyl alcohol and yttrium tri-methoxide. [Si–Y–O–C–N] amorphous powders yielded a unique fibrous microstructure by heat treatment in N2 at 1800 °C. The fibrous microstructure was composed of β–Si3N4 whiskers of submicron in diameter and more than 10 μm in length. Fully dense Si3N4 –SiC–Y2O3 ceramics were also fabricated by heat treatment at 1800 °C followed by powder-vehicle hot pressing at 1700 °C. After these two-step processings, [Si–Y–O–C–N] amorphous powders yielded a unique fine-grained microstructure composed of submicron grains with high aspect ratio.

Si3N4–TiN–Y2O3 ceramics derived from chemically modified perhydropolysilazane

1999 ◽  
Vol 14 (11) ◽  
pp. 4294-4301 ◽  
Author(s):  
Yuji Iwamoto ◽  
Ko-ichi Kikuta ◽  
Shin-ichi Hirano
Keyword(s):  
Heat Treatment ◽  
Hot Pressing ◽  
Titanium Tetrachloride ◽  
Fine Particles ◽  
Size Range ◽  
Fine Grained ◽  
Chemically Modified

[Si–Y–Ti–O–C–N] multicomponent powders were synthesized by pyrolysis at 1000 °C, in NH3 flow, of chemically modified perhydropolysilazane using yttrium triisopropoxide and titanium tetrachloride. [Si–Y–Ti–O–C–N] powders yielded uniform and fine-grained Si3N4–TiN–Y2O3 ceramics by heat treatment at 1800 °C in N2. The fully densified Si3N4–TiN–Y2O3 ceramics were also synthesized by heat treatment at 1800 °C, followed by powder-vehicle hot pressing at 1800 °C in N2. The resulting ceramics revealed that TiN was dispersed as particles having a size range of about 60–600 nm and the fine particles less than 80 nm were dispersed within the β–Si3N4 matrix grains.

Pattern Collapse of High-Aspect-Ratio Silicon Nanostructures - A Parametric Study

2016 ◽  
Vol 255 ◽  
pp. 136-140 ◽  
Author(s):  
Nandi Vrancken ◽  
Guy Vereecke ◽  
Stef Bal ◽  
Stefanie Sergeant ◽  
Geert Doumen ◽  
...  
Keyword(s):  
Aspect Ratio ◽  
High Aspect Ratio ◽  
Silicon Nanostructures ◽  
Complete Structure ◽  
Chemically Modified ◽  
Chemically Modified Surfaces ◽  
Modified Surfaces ◽  
Wet Processing ◽  
Modification Of The Surface

This work focuses on capillary-induced collapse of high-aspect-ratio silicon nanopillars. Modification of the surface chemistry is demonstrated to be an efficient approach for reducing capillary forces and consequently reduce pattern collapse. Special effort is spent on determination of the wetting state of chemically modified surfaces as complete structure wetting is of utmost importance in wet processing. In light of this, an ATR-FTIR based method has been developed to unambiguously distinguish between wetting and non-wetting states.

Metal Alkoxide Synthesis of Glasses and Glass-Ceramics

1985 ◽  
Vol 57 ◽  
Author(s):  
Charles H. Drummond
Keyword(s):  
Hot Pressing ◽  
Low Temperatures ◽  
Glass Formation ◽  
Glass Ceramics ◽  
Base Hydrolysis ◽  
Metal Alkoxide ◽  
Metal Alkoxides ◽  
Fine Grained ◽  
Amorphous Powders

AbstractMetal alkoxide syntheses of the general form or can be used to form soluble alkoxides of most metals. Mutual solution of these alkoxides followed by acid or base hydrolysis, drying and calcining results in the formation of fine-grained (<10Å) amorphous powders at low temperatures. Subsequent hot-pressing or calcining leads to densification and/or crystallization. Compositions in the MgO-Al2O3-SiO2 system with ZrO2 contents to 30 mol% are discussed. Also glass formation of transition oxides derived from metal alkoxides of Hf, Zr, Y and Nb in various combinations are presented.

Effect of Electrolyte Composition in Electrochemical Synthesis of Self-Organized Tio2 Nanotubes

2011 ◽  
Vol 364 ◽  
pp. 298-302 ◽  
Author(s):  
Chin Lim Ying ◽  
Zulkarnain Zainal ◽  
Mohd Zobir Hussein ◽  
Weetee Tan
Keyword(s):  
Heat Treatment ◽  
Aspect Ratio ◽  
High Aspect Ratio ◽  
Treatment Condition ◽  
Aqueous Electrolyte ◽  
Heat Treatment Condition ◽  
Electrolyte Composition ◽  
Electrochemical Anodization ◽  
Self Organized ◽  
Neutral Electrolyte

In this paper, self-organized TiO2 nanotubes (TNT) were synthesized by electrochemical anodization in different electrolytes comprising acidic fluorinated aqueous electrolyte and organic neutral electrolyte. The structural, morphological and composition of TNT were characterized with XRD, FESEM and EDX. Compared with aqueous electrolyte, much smoother tubes with an increase of over 30 times in nanotube length can be obtained by anodization in organic electrolyte. Besides the high aspect ratio, variation of nanotube length within the array could be observed. Interestingly, under the same heat treatment condition, choice of electrolyte has an influence on the crystalline structure of TNT.

Microstructural Development in Nb-Ti Multifilamentary Superconductors During Processing

1985 ◽  
Vol 43 ◽  
pp. 190-191
Author(s):  
A. W. West
Keyword(s):  
Heat Treatment ◽  
Critical Current Density ◽  
Copper Matrix ◽  
Wire Drawing ◽  
Heat Treatments ◽  
Microstructural Development ◽  
Final Size ◽  
Density Values ◽  
The Wire ◽  
Multifilamentary Superconductors

The influence of the filament microstructure on the critical current density values, Jc, of Nb-Ti multifilamentary superconducting composites has been well documented. However the development of these microstructures during composite processing is still under investigation.During manufacture, the multifilamentary composite is given several heat treatments interspersed in the wire-drawing schedule. Typically, these heat treatments are for 5 to 80 hours at temperatures between 523 and 573K. A short heat treatment of approximately 3 hours at 573K is usually given to the wire at final size. Originally this heat treatment was given to soften the copper matrix, but recent work has shown that it can markedly change both the Jc value and microstructure of the composite.

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